1. Field of the Invention
The present invention relates generally to implantable medical apparatus and more specifically relates to a cardiac pacing lead having structure for dispensing chemical agents.
2. Discussion of the Prior Art
Electrodes exist which dispense chemical agents. U.S. Pat. No. 623,022 issued to Johnson teaches an early drug dispensing electrode. More recent drug dispensing electrodes are taught by U.S. Pat. Nos. 3,533,403; 3,680,544 and 3,817,241 issued to Woodson, Shinnick and Grausz, respectively. However, all of these devices are suitable for acute use only and are not usable for chronic implantation.
What is desired is a chronically implantable transvenous cardiac pacing lead having the capability for discretionary chemical treatement to enhance pacing therapy. Tests have shown that pacing thresholds can be substantially lowered using treatment of endocardial tissue by steroids and other chemical agents. Notice that the important feature for such a technique is the dispensing of the drug to the same tissue which is receiving the electrical stimulus. It is for that reason that the chronically implantable drug dispensers taught by U.S. Pat. Nos. 3,527,220; 3,692,027 and 4,146,029 issued to Summers, Ellinwood, Jr. and Ellinwood, Jr., respectively are not acceptable for this purpose. Furthermore, these chronically implantable drug dispensers are far more complex than is required here since they automatically dispense drugs over a relatively long period of time. The present invention, though chronically implantable, provides only discretionary drug therapy by direct action of the attending physician.